Abstract

Many layered superlattice materials intrinsically possess large Seebeck coefficient and low lattice thermal conductivity, but poor electrical conductivity because of the interlayer transport barrier for charges, which has become a stumbling block for achieving high thermoelectric performance. Herein, taking BiCuSeO superlattice as an example, it is demonstrated that efficient interlayer charge release can increase carrier concentration, thereby activating multiple Fermi pockets through Bi/Cu dual vacancies and Pb codoping. Experimental results reveal that the extrinsic charges, which are introduced by Pb and initially trapped in the charge-reservoir [Bi₂O₂]²⁺ sublayers, are effectively released into [Cu₂Se₂]²⁻ sublayers via the channels bridged by Bi/Cu dual vacancies. This efficient interlayer charge release endows dual-vacancy- and Pb-codoped BiCuSeO with increased carrier concentration and electrical conductivity. Moreover, with increasing carrier concentration, the Fermi level is pushed down, activating multiple converged valence bands, which helps to maintain a relatively high Seebeck coefficient and yield an enhanced power factor. As a result, a high ZT value of ∼1.4 is achieved at 823 K in codoped Bi_0.90Pb_0.06Cu_0.96SeO, which is superior to that of pristine BiCuSeO and solely doped samples. The present findings provide prospective insights into the exploration of high-performance thermoelectric materials and the underlying transport physics.

中文翻译：

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高性能层状热电材料的高效层间电荷释放

摘要

许多层状超晶格材料本质上具有较大的塞贝克系数和较低的晶格热导率，但由于电荷的层间传输势垒，其导电性较差，这已成为实现高热电性能的绊脚石。在此，以 BiCuSeO 超晶格为例，证明了有效的层间电荷释放可以增加载流子浓度，从而通过 Bi/Cu 双空位和 Pb 共掺杂激活多个费米袋。实验结果表明，由 Pb 引入并最初被困在电荷库 [Bi ₂ O ₂ ] ²⁺亚层中的外在电荷有效地释放到 [Cu ₂ Se ₂ ]²⁻亚层通过 Bi/Cu 双空位桥接的通道。这种有效的层间电荷释放使双空位和 Pb 共掺杂 BiCuSeO 具有增加的载流子浓度和电导率。此外，随着载流子浓度的增加，费米能级被压低，激活多个收敛的价带，这有助于保持相对较高的塞贝克系数并产生增强的功率因数。因此，在 823 K 的共掺杂 Bi _0.90 Pb _0.06 Cu _{0.96 中}实现了 ~1.4的高ZT值SeO，优于原始 BiCuSeO 和单独掺杂的样品。目前的发现为探索高性能热电材料和潜在的传输物理学提供了前瞻性的见解。